What Is the Difference Between FAP and HNPCC?

Number of genes mutated. In FAP, there is only one gene, the APC gene, which is abnormal. In HNPCC, there are several gene, mutations which may be responsible for the development of the condition.

Presence of polyps, or growths that can become cancer. FAP is characterized by the presence of more than 100 benign polyps. In HNPCC, affected people have fewer polyps, but these polyps can become cancerous more quickly than normal.

Other Forms of Inherited Polyposis Syndromes

There are other, very rare forms of inherited polyposis syndromes that are associated with an increased risk of colorectal cancer. These include:

Juvenile polyposis (JP). Patients may have anywhere from 5 to 500 polyps, or growths, mostly in the colon and rectum, which usually begins before the age of 10. The stomach and small intestine are less commonly affected. These patients are also at increased risk of bowel cancer.

Peutz-Jehgers syndrome (PJS). Patients with PJS typically develop dozens to thousands of benign polyps, or growths, in the stomach and intestines, primarily in the small intestine. The growths can become malignant or can cause obstruction of the bowel.

Ashkenazi Jews and Colorectal Cancer

Jewish people who are Ashkenazi, or of Eastern European descent, are at increased risk for colorectal cancer. This is thought to be due to a variant of the APC gene that is found in 6% of this population. Ashkenazi Jews make up the majority of the Jewish population in the U.S.

If you suspect that you are at risk for an inherited form of colorectal cancer, talk to your doctor. There may be a genetic test that can be performed to confirm your suspicions.